<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>外间距</title>
</head>
<style>
    body {
        margin: 0;
    }
    .fu {
        background-color: rgba(255,255,0,0.3);
    }
    .fu>div{
        width: 100px;
        height: 100px;
        background-color: rgba(0,0,255,0.6);
        border:2px solid #00f;
        color:#fff;
        font-size: 25px;
        font-weight: bold;
    }
    .z1 {
        margin-bottom: 30px;
    }
    .z2 {
        margin-top:50px
    }
    span {
        border: 2px solid #f00
    }
    .s2 {
        margin:30px /*行内元素垂直方向的外间距不生效 */
    }
</style>
<body>
    <span>span1</span><span class="s2">span2</span><span>span3</span>
    <div class="fu">
        <div class="z1">子元素1</div>
        <div class="z2">子元素2</div>
        <div class="z3">子元素3</div>
        <div class="z4">子元素4</div>
    </div>


</body>
</html>